Flies from the Amber Author:Wil McCarthy Forty light years from earth the colonists on the world of Unua have somehow managed to keep civilization strugling on despite twice daily earthquakes and technology lagging far behind that of the mother planet. But now an Unuan mining expedition has discovered and alien mineral they name centrokrist- a stone of incomparable beauty.
A pretty good read.If you are familiar with black hole physics.The author brought up some fascinating problems if you are trying to fight a battle near a black hole , how time itself can become an ally or enemy.